1. Field of the Invention
The present invention relates to a process for the preparation of catalyst compositions with a particle diameter in the range 20–2000 microns.
2. Prior Art
For several catalytic applications, such as fluidized bed processes, small catalyst particles are required. Such particles are generally produced by spray-drying a mixture of the catalyst ingredients. For instance, fluid catalytic cracking (FCC) catalysts are generally prepared by spray-drying an aqueous slurry of zeolite, clay, and silica and/or alumina.
Spray-drying involves pumping a slurry containing the catalyst ingredients through a nozzle (a high-pressure nozzle or a rotating wheel with nozzle) into a chamber heated with hot air. During this process, high shear is placed on the slurry, thereby creating small droplets that quickly dry in the heated chamber.
Depending on the type of nozzle used, the particle size distribution of the resulting catalyst particles depends on either the nozzle pressure or the rotating speed of the wheel, but generally lies in the range of 30–90 microns.
Unfortunately, only slurries with a low solids content (i.e. below about 45 wt % solids) and, consequently, a high liquid content can be spray-dried. Slurries with a higher solids content either are too viscous to be pumped through the nozzle or will not give suitable droplets upon spraying.
Due to this low solids limitation, large volumes of liquid are required, which have to be evaporated during the drying step. This is energy inefficient.
This problem is solved by the process according to the present invention.